I'm not sure what you are trying to contribute. The Salas regulator is a good design for a number of tasks. It is not quiet enough to get the best performance from a low phase noise oscillator. The voltage stability over time and temperature can also shift the fundamental frequency of a precision oscillator, possibly enough to affect some applications.
The simple regulator above does not have the lowest output impedance and a number of other limitations but it has very high line noise rejection and a very low noise floor both important for getting the most performance from a very high quality crystal oscillator and it does it using 3 active components. Depending on its application more parts can get small improvements but at some point the improvements do not propagate through to the regulated circuit.
The simple regulator above does not have the lowest output impedance and a number of other limitations but it has very high line noise rejection and a very low noise floor both important for getting the most performance from a very high quality crystal oscillator and it does it using 3 active components. Depending on its application more parts can get small improvements but at some point the improvements do not propagate through to the regulated circuit.
Demian, i think i have the right transistors here to try your circuit and as i have said, i intend to. but i'm wondering can you recommend any other small signal transistors in case? its been a while since i used the 2n3904 etc and they are probably well buried in my parts bin. I know i have bc860/50. also i have the 431 in soic8, but i have plenty of other low noise references too, i will toy with some others. is the schematic on the previous pages the latest or should i search the widget thread?
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I used the 2N3904 because its in my bin and has lower noise than a 2N4401 but not by much. Almost any small signal transistor will work with the best possibly 3 dB better than the worst. The low impedance of the reference (470 uF) means that the current noise is not significant. The TL431 is used more like a servo to correct for the changes in Vbe due to load and temperature, it is not the reference that the system is correcting to in the audio band.
The schematic is current I believe. There is some potential for lower output Z with a higher bias current in Q1, but it won't affect a crystal oscillator and it will add more power consumption. Let us know how it goes.
The schematic is current I believe. There is some potential for lower output Z with a higher bias current in Q1, but it won't affect a crystal oscillator and it will add more power consumption. Let us know how it goes.
thanks for the info, is there any advantage to be gained from making the 470u as low impedance as possible? or any old polymer ok? i take it the 1u on the output is film? so i take it an LM317 could be used in the same way to servo the vbe as the 431? not that I would, just thinking it through, I tend to learn more from doing. after knocking this up on perf i like the idea of a really tiny version using the sot23 431, BC850/60 and smd everything. i figure it could be made pretty small; allowing more ideal placement
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It'd be nice to see small PCBs for Demian's clock regs.
Group buy material, IMHO!
That's good idea.
Hi Demian,
I did some simulation to your reg and shown pretty good result. I'm thinking about design a prototype PCB for real evaluation. But it should be under your promise.
Ian
My test board
Attached is a zip of he expresspcb file I used to test the design concepts. It incorporates an input regulator to handle short circuit protection etc. the regulator circuit supporting two dip oscillators and the transformer coupled output to prevent the system grounds from undoing all the work.
I won't have a chance to create a schematic for it but by careful inspection that should not be necessary. Its offered as a starting point, not as an end in itself.
The basic regulator was first published by someone else (I have lost the reference) and my addition is the TL431 servo.
Don't trust this, study and verify (I may well have made mistakes) and build on it.
Attached is a zip of he expresspcb file I used to test the design concepts. It incorporates an input regulator to handle short circuit protection etc. the regulator circuit supporting two dip oscillators and the transformer coupled output to prevent the system grounds from undoing all the work.
I won't have a chance to create a schematic for it but by careful inspection that should not be necessary. Its offered as a starting point, not as an end in itself.
The basic regulator was first published by someone else (I have lost the reference) and my addition is the TL431 servo.
Don't trust this, study and verify (I may well have made mistakes) and build on it.
Ian asynchronous I2S and S/PDIF FIFO KIT group buy is running at GB area
Just a kindly reminder that the Ian asynchronous I2S and S/PDIF FIFO KIT group buy is running. Please go the group buy area for details:
http://www.diyaudio.com/forums/group-buys/207438-ian-asynchronous-i2s-s-pdif-fifo-kit-group-buy.html
I will continue this thread for technical issues, new progress may include:
1.Trying suitable low noise power supply for oscillators and FIFO project.
2.New Si570 based clock board.
3.I2S and S/PDIF FIFO applications.
4.Possible battery based power supply with charging management.
5.Technical supplort
…….
Have a nice week.
Ian
Hi Ian, I'm still reluctant to buy the otherwise very impressive FIFO kit as I'm unsure about how easy it is to leave out the LDO and to power the clock(s) with a very low noise regulator.
- Do you supply a schematic with the kit?
- Does the dual clock board have one LDO per clock?
I see in your previous post that you are investigating a low noise power supply. Would that mean having it on (newly designed) boards or add on?
- Do you supply a schematic with the kit?
- Does the dual clock board have one LDO per clock?
I see in your previous post that you are investigating a low noise power supply. Would that mean having it on (newly designed) boards or add on?
Si570
Does someone enlighten me about the performance of the Si570 down to 10Hz offset and at clock rates we need in this project (i.e. around 25 MHz)?
I can find phase noise spec for clock frequencies above 100MHz and down to an offset of 100Hz.
However those values are significantly less good than eg. the Crystek CCHD-957 Model or a Tentlabs clock at 100Hz offset and lower (i.e. suitable for this project) clock frequencies.
Does someone enlighten me about the performance of the Si570 down to 10Hz offset and at clock rates we need in this project (i.e. around 25 MHz)?
I can find phase noise spec for clock frequencies above 100MHz and down to an offset of 100Hz.
However those values are significantly less good than eg. the Crystek CCHD-957 Model or a Tentlabs clock at 100Hz offset and lower (i.e. suitable for this project) clock frequencies.
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Hi zinsula,
The easiest way to evaluate and connect an external low noise power supply is using the IC socket as an adapter, just as what I did before to evaluate the battery power supply.
http://www.diyaudio.com/forums/digital-line-level/192465-asynchronous-i2s-fifo-project-ultimate-weapon-fight-jitter-24.html
After you making sure the external power supply is good enough, you can connect them to the dual XO board by just removing the filters or the LDOs. It’s not a difficult job, especially for you J.
For a very skilled DIYer like you, what I recommended is configuring a FIFO with external clock, (please see the user guide for detailed) which is not suggested for the normal users. So that, you can design your own power supply and clock and do not have to be limited by my board. Although I couldn’t guarantee my clock board is the best, but it truly based on long time testing and optimizing. You could keep it as a reference, by comparing with it, you will know by how much your improvement is achieving.
Once I have time, I’ll design a prototype PCB for Demian’s reg. I could send a couple of that PCB to you for free to make some evaluation if you like.
Ian
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Thank you Ian. This could well be an option, but if using an external clock, the "comfortable" automatic clock switching is lost.
Primarily, I'd plan to connect the FIFO to a multi format DVD player, which puts out both the 44.1 and the 48kHz - Family of sample rates.
But I'll take one...
Primarily, I'd plan to connect the FIFO to a multi format DVD player, which puts out both the 44.1 and the 48kHz - Family of sample rates.
But I'll take one...
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it will be interesting to put Demians regulator up against Jung's AD797 based circuit from the old Electronic Design article from analogue devices 'how to build an ulra-low noise reference' which has noise estimated at 1.25nV/(2^root)Hz (not sure how to make the square root symbol with normal text)
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